Editing Subdural hematoma (section)

==Diagnosis==
[[Image:Ct-scan of the brain with an subdural hematoma.jpg|thumb|A subdural hematoma demonstrated by CT]]
[[File:ChronicSubduralPostBurrHoles.jpg|thumb|Chronic subdural after treatment with [[burr hole]]s]]
It is important that a person receive medical assessment, including a complete [[neurology|neurological]] examination, after any head trauma. A [[CT scan]] or [[MRI scan]] will usually detect significant subdural hematomas.{{citation needed|date=February 2021}}

Subdural hematomas occur most often around the tops and sides of the [[frontal lobe|frontal]] and [[parietal lobe]]s.<ref name="wagner" /><ref name="UVT" /> They also occur in the [[posterior cranial fossa]], and near the [[falx cerebri]] and [[tentorium cerebelli]].<ref name="wagner" /> Unlike epidural hematomas, which cannot expand past the [[skull suture|sutures of the skull]], subdural hematomas can expand along the inside of the skull, creating a concave shape that follows the curve of the brain, stopping only at [[dural reflection]]s like the tentorium cerebelli and falx cerebri.{{citation needed|date=February 2021}}

On a CT scan, subdural hematomas are classically crescent-shaped, with a concave surface away from the skull. However, they can have a convex appearance, especially in the early stages of bleeding. This may cause difficulty in distinguishing between subdural and epidural hemorrhages. A more reliable indicator of subdural hemorrhage is its involvement of a larger portion of the cerebral hemisphere. Subdural blood can also be seen as a layering density along the tentorium cerebelli. This can be a chronic, stable process, since the feeding system is low-pressure. In such cases, subtle signs of bleeding—such as effacement of [[sulcus (neuroanatomy)|sulci]] or medial displacement of the junction between [[gray matter]] and [[white matter]]—may be apparent.{{citation needed|date=February 2021}}

{|class="wikitable" align="right"
|-
! Age !! Attenuation ([[Hounsfield units|HU]])
|-
|  First hours || +75 to +100<ref name="Rao2016">Fig 3 in: {{Cite journal |vauthors=Rao MG, Singh D, Khandelwal N, Sharma SK |date=April 2016 |title=Dating of Early Subdural Haematoma: A Correlative Clinico-Radiological Study |journal=Journal of Clinical and Diagnostic Research |volume=10 |issue=4 |pages=HC01–HC05 |doi=10.7860/JCDR/2016/17207.7644 |pmc=4866129 |pmid=27190831}}</ref>
|-
| After 3 days || +65 to +85<ref name="Rao2016" />
|-
| After 10–14 days || +35 to +40<ref>{{Cite web |title=Subdural haemorrhage |url=https://radiopaedia.org/articles/subdural-haemorrhage |access-date=2018-08-14 |website=[[Radiopaedia]] |vauthors=Sharma R, Gaillard F}}</ref>
|}

Fresh subdural bleeding is [[radiodensity|hyperdense]], but becomes more hypodense over time due to dissolution of cellular elements. After 3–14 days, the bleeding becomes isodense with brain tissue and may therefore be missed.<ref>{{Cite web |title=Intracranial Hemorrhage – Subdural Hematomas (SDH) |url=http://www.stritch.luc.edu/lumen/MedEd/Radio/curriculum/Neurology/IC_hemorrhage_2013.htm |access-date=2018-01-06 |website=[[Loyola University Chicago]]}}</ref> Subsequently, it will become more hypodense than brain tissue.<ref name="Schweitzer 2019">{{Cite journal |vauthors=Schweitzer AD, Niogi SN, Whitlow CT, Tsiouris AJ |date=October 2019 |title=Traumatic Brain Injury: Imaging Patterns and Complications |journal=Radiographics |volume=39 |issue=6 |pages=1571–1595 |doi=10.1148/rg.2019190076 |pmid=31589576 |s2cid=203926019}}</ref>

===Classification===
Subdural hematomas are classified as [[Acute (medicine)|acute]], subacute, or [[chronic (medicine)|chronic]], depending on the speed of their onset.<ref>{{EMedicine|article|247472|Subdural Hematoma Surgery}}</ref>

Acute bleeds often develop after high-speed acceleration or deceleration injuries. They are most severe if associated with [[cerebral contusion]]s.<ref name="wagner" /> Though much faster than chronic subdural bleeds, acute subdural bleeding is usually venous and therefore slower than the arterial bleeding of an epidural hemorrhage. Acute subdural hematomas due to trauma are the most lethal of all head injuries and have a high [[mortality rate]] if they are not rapidly treated with surgical decompression.<ref>{{Cite web |last=<!--Staff writer(s); no by-line.--> |title=Acute Subdural Hematomas |url=http://neurosurgery.ucla.edu/body.cfm?id=102 |access-date=21 July 2011 |website=UCLA Health}}</ref> The mortality rate is higher than that of epidural hematomas and [[Focal and diffuse brain injury|diffuse brain injuries]] because the force required to cause subdural hematomas tends to cause other severe injuries as well.<ref>{{EMedicine|article|247664|Penetrating Head Trauma}}</ref>

Chronic subdural bleeds develop over a period of days to weeks, often after minor head trauma, though a cause is not identifiable in 50% of patients.<ref name="Downie">Downie A. 2001. [http://www.radiology.co.uk/srs-x/tutors/cttrauma/tutor.htm "Tutorial: CT in head trauma"] {{Webarchive|url=https://web.archive.org/web/20051106231525/http://www.radiology.co.uk/srs-x/tutors/cttrauma/tutor.htm |date=2005-11-06 }}. Retrieved on August 7, 2007.</ref> They may not be discovered until they present clinically months or years after a head injury.<ref name="Kushner98">{{Cite journal |vauthors=Kushner D |year=1998 |title=Mild traumatic brain injury: toward understanding manifestations and treatment |journal=Archives of Internal Medicine |volume=158 |issue=15 |pages=1617–1624 |doi=10.1001/archinte.158.15.1617 |pmid=9701095 |doi-access=free}}</ref> The bleeding from a chronic hematoma is slow and usually stops by itself.<ref name="UVT" /><ref>{{Cite journal |vauthors=Faried A, Halim D, Widjaya IA, Badri RF, Sulaiman SF, Arifin MZ |date=October 2019 |title=Correlation between the skull base fracture and the incidence of intracranial hemorrhage in patients with traumatic brain injury |journal=Chinese Journal of Traumatology = Zhonghua Chuang Shang Za Zhi |volume=22 |issue=5 |pages=286–289 |doi=10.1016/j.cjtee.2019.05.006 |pmc=6823676 |pmid=31521457}}</ref> Because these hematomas progress slowly, they can more often be stopped before they cause significant damage, especially if they are less than a centimeter wide. In one study, only 22% of patients with chronic subdural bleeds had outcomes worse than "good" or "complete recovery".<ref name="wagner" /> Chronic subdural hematomas are common in the elderly.<ref name="Kushner98" />

===Differential diagnosis===
{{Epidural vs. subdural hematoma}}
{{Clear}}